Multipiston motor or pump



March 2 1951 E. F. ENGSTROM MULTIPISTON MOTOR- OR PUMP 3 Sheets-Sheet 1 Filed Dec. 9, 1947 9 '272512 Dr 92 [emu-f: Evssreon Marbh 1951 E. F. ENGSTROM MULTIPISTON MOTOR- OR PUMP- 3 Sheets-Sheet 2 Filed Dec. 9, 1947 -mn DP felvsr FfiGSrEQM March 20, 1951 E. F. ENGSTROM 2,545,609

MULTIPISTON MOTOR 0R PUMP Filed Dec. 9, 1947 5 Sheets-Sheet 3 in; k

embod ent; ther Patented Mar. 20, 1951 PAT '1? o 2;,545,6Q9;

UL'rrPrs-rro-N MOTOR on PUMPI- f-e t: ines impse I Aggfiegtion} m m r 9, 1947; Serial No. 7903625 c1.:w r*1=:ie 1

The present invention relates to; improvements in hydraulie motors 01 pumps and: more; pare ticulariy concerns a mu 1ti=pisten device"v of this character-L An important; object 01'; the present invention to provide animpnoved; compact; 105v. cost; highly, efiie'ient; hydaraulie motoror pump adapt.- edtoibez made inrsmallt sizes Another object at the invent-mil" is to provide a muithpiston; hydraulic? motor on pump-10f high conversion efiiciency that. is,. such a devise which the power loss ratie; due to, irrational resistanceuor; back pressures; are. redueed ta pliaaG-r h ar minimum. and whiehi unusually hi h rate of: work or power; output in relation: to: the poweemputisattained.

Atutthen qbiect; of the iny nt'en. is: to" nr yide nevel over-lemme; thr st; mum-me e mete Qrpumpm it;

anoth obieqt iie eve i e s 9, em-

s ill qhieei; Q' the s 9 1: d? aeimiymved s nwl emu ,i-mswn e: Ze emQ -pr 12m i V I It s e se are Ql ii e n nt on e preiEd n imew eame 2 Q making-a h d ants fluid" istr b to i e m m-piston hydraulic m t r r p p.-;

Qther bi c present ip ver tiph will be readily, apparent from the fb l wins de ai d ss r mi mf a r ferr k n. n. c mgumztibn with .,-i 2. i heets. of draw ngs in th ecqm ami he 1i? 1 Figure. 1, is; a; side eievat-ibnal viewof a by; Qra lic m tor qr pumptnit mb y ne he uites lfi t e inve 'itiqn;

F e r-e .11s a rear a d Q Yat waM e st o h umn ir ureu features and dva e Q L t n Figure 3, is a fronte dr elevatior at View: of the ikle'fl fii E sune s n enlar ed ea i itmuralv ecii e view th ough he unit on th l e L o .E ur tc I ur 2 s. ran verse e tion l v ew hmusb the: uni tak n, subsiautiem; 011', the; ine: vii-4V Qf. Ii use 5;. -i Eieure s. tr nsverse ses jge v ew taken jsu zstamiallx Vile-V Qf Fi ur distliibutorstructure;

Figure 11-3: is: enlarged sidef. elevatiohar view? otthe cam. gazoove ring; element or the unit; and

Eigure; 1 4 is: a. fragmentary seetional: view; taken the plane 02- line oi Eige 1115613.

By: the: present invention a hydraulic 11101391; or pump is: provided having a minimum: mm}; ber ofoperating parts: which are of relatively simple, easily; fabricated charac r; afferent; unusualeompaetness in. assembly; and efiiciemyi. ruggedness. and di liabil iri 1m 0D ?&fiiQIl;-. construction and; operational characteristics are such; cr' over, t at. ex eptionalia smooth and u iform; fiunctipnali and hieh: adin ehanaet s stics'areattained fo z thistype Qfun twhen p natme as amni n. hvdraukie fluid: um ie hi h pressure is pplied; a he unit. and is translated thereby into rotary power. EaGiz ifiies are. provided" for operating; the; unit with equar efificiency in reverse, and reversal may be efiected; as nearly: as practicable instantaneously; Where the. unit is utilized as a pump, rotary: power in! put is translated into hydrauiic. fluidpressute; N131 alteration whatsoever-'- is required for using the. unit either as. a motor or a pump; the only alternative being Whether hydraulic fluid;- is to be supplied to the unit tor aetivating the sameer Whether the. unit is toer'eate: hydraulm fluid pres sure. in eitheruse or the ur i-itactuation thereof is smooth, uni-form and powerful, there being ing or casingfl a; plurality of reeiprqclahle Qistons l-B qperableqn axes, ar aHeI ta and in c i centric series about the shaft l-5 being arr to drive the'sarne' where the unitis qpeifatipg as a motor; to be qiivai'eq br ue l the: medi m Qi the. s a t W the u t Qeerai ne as a. 19 ins, tq isiqnismede er q meq ne the;

der head bores 3 I in a hydraulic fluid circuit through a pair of similar, independent ports [9 and 20 which open through the casing I'I (Figures 1 and 4). One end of the shaft l5, which will herein be referred to as the front end, has an extension 2| which projects beyond the front end of the casing l1 and is adapted to have secured thereto through use of a longitudinal keyway 22, means such as a pulley or gear (not shown) for connecting the same with associated apparatus.

Within the housing II, the shaft I is supported rotatably by front and rear antifriction bearing assemblies 23 and 24, respectively. In the present instance, these are ball bearing assemblies. The forward bearing assembly 23 is preferably larger than the rear bearing assembly 24 and is capable of longitudinal loads, thus serving also as a thrust bearing.

Each of the pistons I8 is preferably identical with each of the others and there may be as many of the pistons IB spaced in concentric series about the shaft l5 as preferred. In the present instance, the unit has ten of the pistons 18 (Figure 7) which are double acting and have opposite blunt ends affording compression heads each of which is adapted to receive or impart a thrust. As best seen in Figure 4, each of the pistons I8 is of uniform cylindrical shape throughout its major extent and is formed with a narrow medial annular, radially extending thrust rib or shoulder formation 25 of substantially larger diameter than the opposite body portions of the piston. The opposite faces of the annular thrust shoulder formation 25 are finished to a preferred equal taper. In practice a 30 taper has been found highly desirable.

At their forward ends the pistons are slidably guided in respective closely fitting bearing bores or'cylinders 21 which open rearwardly into coaxial thrust shoulder clearing bores 28 and at their forward ends into enlarged pressure chamber or cylinder head bores 29. The rear end portions of the piston l8 are closely slidably bearing in coaxial cylinder bores 30 which extend from the thrust shoulder clearance bores 28 and open into enlarged rear end pressure chamber cylinbores 21 and 30 are so roportioned to the lengths of the respective opposite cylindrical portions of the pistons l8 and are spaced such an axial distance apart that in each reciprocable cycle of theassociated piston I8 the compression head terminals of the piston will move between extreme limits into the pressure chambers 29 and 3|.

."The lengths of the piston strokes in each direction are determined by a thrust transmission member 32 on the shaft l5 cooperating with the thrust shoulder formations 25 of the pistons. AS best seen in Figures 4 and 13, the transmission member 32 is in the form of a sleeve or ring provided witha transmission cam groove 33 which is preferably of complementary cross-sectional shape to the tapering shape of the an- ;nular piston thrust shoulder formations 25 so that there is a close bearing relationship therebetween and especially between the opposing tapering thrust surfaces thereof. This is accomplished by generating the groove 33 with a cutter of the same profile as the shoulder formation 25 and held, while cutting, in the same relative position as one of the pistons l8 with its thrust shoulder 25. Looseness, lag or slap in operation are thus avoided.

' The transmission groove 33 is of generally spiral form and where, as in the present instance,

The lengths of the bearing it is desired to have each of the pistons 18 make two complete reciprocal thrust cycles in each revolution of the shaft I5, the groove comprises equal sections extending about the cam ring in respective reverse directions and with uniform pitch. Thus, in each revolution of the shaft l5, each of the pistons I8 must travel reciprocably to its full opposite reciprocal limits twice, and since the pistons are double acting the ten pistons will be responsible for forty thrusts for each shaft revolution. Furthermore, since the piston thrust ribs or shoulders 25 and the groove 33 are in relatively close bearing relation, the pistons will rotate as the thrust shoulders 25 thereof follow the groove, thereby minimizing wear due to friction.

Hydraulic fluid communication between the ports I9 and 25 and the pistons i8 is effected through a distributing system including structure which herein comprises part of the shaft l5. To this end the shaft is provided between a reduced rear end bearing pilot terminal portion 34 and a front end integral bearing collar 35 with a cylindrical distributor portion 3! of substantial length which is of slightly smaller diameter than the bearing collar portion 35 but of substantially greater diameter than the rear end bearing pilot terminal 34. Formed equidistantly spaced in the portion 31 (Figures 1, 5 and 10) are four coextensive, parallel, identical, generally longitudinally extending fluid distribution channels or grooves 38, 39, 4d and 4 I. The grooves are of substantial width and preferably have flaring side walls so that they are of the greatest width at the periphery of the shaft portion 31 with, however, substantial land areas between adjacent grooves. The rear portions of the grooves are in straight parallelism. Approximately midway their lengths, the grooves are equally angled to assume respective spiral form in their forward portions to extend 90 around the shaft portion 31. Completely encircling and enclosing the grooved intermediate distributor portion 31 of the shaft is a coextensive distributor sleeve 42 which is secured to the shaft portion 31 in fluid tight relation and forms a closure for the respective grooves. As best seen in Figures 4 and 5, the sleeve 42 is formed adjacent its rear end, and thus the rear ends of the distributor grooves, with diametrically opposite transverse slots 43 and 44 which register with two of the grooves, for example, the grooves 39 and 4|, respectively. The ends of the slots are formed with an even greater angular flare than the walls of the grooves with which they register whereby to provide large free entry or escape ports, as the case may be, for hydraulic fluid with respect to an annular fluid communication groove or channel 45 in the wall of the casing slidably encircling the sleeve 42 at the port slots. The channel 45 communicates by way of a duct bore 41 with the fluid port 20.

' Spaced forwardly from the fluid orifice or port slots 43 and 44, is another pair of diametrically opposite fluid orifice or port slots 48 and.49 which are located 90 angularly from the first mentioned slots 43 and 44, respectively. The slots 48 and 49 which identified by the numeral 52, and which respectively open into the grooves 38-, 39 40 and q litFigure e' and 7) These slots; 52 are adapted tip-register successively with and afford commu-nication between the respective distributor grooves and individual, relatively narrow; radial coma munication ducts 53* which lead from the respecti-ve pistonpressure chambers St to the closely s l idably fitted surrounding bore wall within which the distributor sleeve 42 is rota-table withthe shaft i5; J

Gommunicatio'n'; between the several distributor grooves and the forward end pressure chambers for the pistons is eiiect'ed through radial passages 54 leading therefrom through the, bore wall slidably engagingthe sleeve adjacent the f or'ward distribution grooyes38 39 40 and U c'hi (referring to; Figures 4 and 9') ctive communication orifice slots 55" open t ough the sleeve *2: Erqrn; Figures 7; and; 9 it will be observed that" the radial communication ducts 53 and 54 are slightly narrower than the land areas ofthe sleeve dfi'intervening between the respective orifice or portslots 52 and 55 Further, it will be observed- 'h i th o s 5 an ii, r o a or' i length w respect to the perimeter of the, sleeve 42 to Q. ji hhih e s mul aneous y i eac n n p. o he ra a pre sure: chamb r d cts 53 v, sn .q el A's a esult each; o i h htq t r qvcs at allltimssi ommu ca on li ree? essure. hambe 3" o of he a 9% an h ng for ar lc r ss i .v ha b rs o t o; l fier ht one o he? Pistons ,0? r mo ed? n he; ircc iqno p ra ff e. r ss h ei ver ar n 13. the; s hhs '8; a tour Qf; thsdi iributh qoyesj ei ht o he: pis ons w ll; be d r h drau ic; thr st 9a 1 2 r h o e. dir cti h. d. l ur n h RDO irec ion. y; alterhh s: hai un or l a: .nd" h st n rcuitl is l aves. ne. a f d amsir ca i vo p it hhihhsin ev oper in nte al ow r ng Q n r l. Wh le ch ng n hru t direc i n; as de itsverseits hr shd re iica hl t c wor s, avins re nce zfi sur lrzla re; hev lands etween thasl s s dih togthe oo es, nd; 441: at one. Side and b'etwe ,thegroo s 39 arid .0 at he llhosi cside n, cut-0 t r ation to res ectiv hq uhicah n duc s .3 matio of h ha 6? n: ther eq ph l is lace uch ds n rshde i c a d around. betwce th l slotsle d fhs thsrcove man .1 one s d a the an betijveen theslots l'e ng tothe grooves Land ill at he oh cs iei i i eq ive p neu ralizin ut Off; hhl ah h y here. s co rdin ed he trali'z ing cut-off action by-the landsbetwcfinthe Q 'b ri lo s 5 a he. opp e end of t n' s'eriesf, asshown in Fig; .9

6 a. slightly enlarg"edediameter intermediate pon tic-n 58- (Eigures 4a and 8% to which the groovedsleeve 32 is fixedly attached and secured. against any possible rotationby means of a key 58a.

In fabricating the shaft is and the distributor assembly thereof, the shaft is first turned down at. least to provide the bearing collar 35. and the distributor section 31.. It is then formed with the distributor grooves 38', 39; iii and Ail, and withthe heywayi 22: which, it will be observed in Figures 4 and 19,; is disposed with its; longitudinal center 45'9 from the adjacent end axes of two of the distributor grooves; herein the grooves 39' and: 411i Thereafter the sleeve 42 is pressefitted 7 into enclosing relation'onto, themtermediate dis? tribntor portion 31- of the: shaft, with the forward; end of the sleeve abutting.- the rearward shoulder defined by.- thebearingcollar 35:. Thorough fluid= proofing of the sleeve 42 with respect to all on gag ed areas: of the shaft portion ET is effected;

V by means such as copper brazing. The shaft and sleeve thus become an integral unit. Breferably after this, the sleeve s2 is turned down to provide the larger diameter control ring receiving por-l tion 58; Then the several orifice slots communicating through the: sleeve 62 with the distri'a bution grooves in the shaft are cut asby milling the same; the keyway- .22 affording a convenient guide for proper disposal of: the several slots;

. After the assembly is then appropriately further machined and ground, if" that still necessary, depending upon. preferred shop. practice, thecam groove ring 32' is press fitted onto the sleeve por-- tion 53; and keyed in place. and the completed shaft and distributor assembly is ready tobe assembled with the casing I1. I

For convenience in fabrication and assembly the casing Iii; is preferably made in a plurality of; stacked or coaxially assembledsections. These sections will be described substantially inthe orderin, which assembly thereof is adapted to, be efiected.

The rear endof the casing I1 is in the: form of; a; section 592 which has formed. therein at diametrically opposite sides: of its: rear face. and opening rearWardl y the hydraulic fluid ports Hiand 2d, the. latter being preferablyappropriatelytapped to have hydraulic fluid ducts (not shown")? fafluid circuit threadedly secured therein. An axial rearward opening 60 in the section 59' gives access into the central shaft. bore thereof for assembling: the. bearing assembly 2.47 which is; press-fitted; into a rabbet, groove 61 in proper: position toreceive the bearing end pilot terminal 3 4, of the, shaft, The opening 60. is preferably closed by a removable sealing plug 62'. The cas-- ing section, 59 is, of; a length to encompass the: di r but r sleeve 42 up to and; nclud n th distributor orifice slots 52, and at its forward: face has the pressurechambers. 3i]. and; the pasag s- 53- orm d therein.-

In ord'er'to isolate the distribution. groove 45; from the chamber for the. rear bearing 24; an expanding-pressure sealing ring 63 is mounted therebetween in a groove 64 inthe shaft bore wall of the casing section- 59. The distributor grooves 45* and so are pressure isolated from one another by a pressure sealing ring assembly 65; in an annular groove (51-, while an isolating pressure; sealing ring assembly 68 is disposed in a groove 69; intervening between the distri h r groo and. heinr ssure chamber du t 5.1.

intermediate'section It which abuts theforward end of the section 59 and has the piston bearing bores 30 and the piston shoulder clearance bores 28 formed therein, as well as an annular chamber II (Figures 4 and 8) affording clearance for the cam groove ring 32 and intersecting the radially inner sides of the piston shoulder clearance bores 28. A pressure sealing ring 12 seated in an annular groove 13 seals the pressure chamber ducts 53 from the chamber II.

Abutting the front end of the section is a piston bearing ring section 14, the principal function of which is to provide the piston bearing bores 21. Forwardly of this the assembly includes a casing ring section I5 which in the rear face abutting the ring section 14 has the compression chambers 29 and the ducts 54 formed therein. Escape of hydraulic fluid pressure from the ducts 54 longitudinally of the shaft is prevented by a sealing ring T! in an internal annular groove 18 in the ring section 14 and a sealing ring I9 in an'internal annular groove 83 in the ring section I5.

At its forward end the casing ring section I5 has an internal rabbet groove SI within which the outer race of the bearing assembly 23 is seated in fixed longitudinal relation to the casing I'I. Since the inner race of the bearing assembly is held fast against a shoulder 82 at the forward end of the sleeve 42, by means of a nut 83 carried by a forward, threaded portion 84 on the shaft, it will be apparent that the shaft is supported in longitudinal thrust relationship by the front bearing assembly 23. A longitudinal keyway 85 is provided for reception of the retaining leg of a conventional bearing lock washer 86 associated with the nut 83. A forward end cap section 86 completes the housing sections and is formed with an internal bearing rabbet groove 8! complementary to the groove 8| for reception and holding of the outer race of the bearing assembly 23. A groove 88 forwardly of the bearing groove 81 affords a chamber for clearing. the nut 83. The forward portion of the cap section 86 has a slidable bearing bore 89 for passage of the'shaft I5, and an expansion type sealing ring 99 is disposed in an internal groove 9| encircling the shaft for preventing leakage of hydraulic fluid past the shaft out of the housing from the front bearing chamber.

Since the intermediate ring sections ID and I of the housing have the bearing bores 39 and 2'3, respectively, for the pistons I8, it is highly essential that these sections be in accurate angular registration, and for this purpose stakes 32 (Figure 8) -may be provided at appropriate intervals.

Use of these aligning stakes permits coaxial boring and lapping of the aligned bearing bores 21 and 39. I All of the sections of the casing are held together in tight assemblyby means such as a plurality of tie bolts 93 (Figures 3, 4 and 7) which are accessible from the front of the unit and have the heads thereof countersunk within counterbores 94 in the cap section 85.

For attachment of the front end of the unit to a supporting structure, the cap section 85 may be provided with an annular radial flange 95 provided with an annular series of spaced axially extending bores 91 for receiving attachment bolts or the like. The rear end of the cap section 85 and the adjacent portion of the housing ring section I5 are provided with external insets 98 for clearing the attachment bolt heads or nuts. Of course, if preferred, any other means may be provided on the unit for attaching it to supporting structure, such as a foot or base or the like, as iscommon practice in mounting motors or pumps.

In the operation of the unit, where it is used as a motor, hydraulic fluid under pressure is introduced either through the port I9 or the port 20, the alternate port then serving as an outlet or exhaust port. Instantaneously upon introduction of the pressure fluid through the port I9, for example, it enters the distributor grooves 38 and which provide passage therefor to the operating zone involving the pistons I8. At the same time the remaining grooves 39 and M serve as return passages for the spent hydraulic fluid. Where the pressure fluid is introduced by way of the port 20 it will, of course, enter and travel by way of the grooves 39 and M to the pistons and return by way of the grooves 38 and 40. The respective orifice slots 52 and 53 leading from the grooves valve the pressure fluid to the respective opposite ends of the pistons I8 to be actuated. By reason of the 90 spiraling of the grooves, the piston ends opposite to the thrust are always in communication with the low pressure or return grooves leading to the exhaust port.

Inasmuch as each of the slots 52 and always, in any angular position thereof, communicates with two pressure chamber communication ducts, there is a continuous and progressive overlapping of piston thrust around the entire circuit, thus assuring smooth, powerful, uniform, vibrationless power transmission to the cam ring 32 and thus the shaft I5, without any possibility of dwell or stalling at any point in the circuit. The motor is therefore capable of instantaneous starting and stopping. Furthermore, it will be readily apparent that the motor is instantly reversible, within the practical limits permitted or required in the associated driven apparatus.

When in use as a pump, the unit is capable of creating hydraulic pressures on the order of those utilized when the unit is operated as a motor. For this purpose, rotary power input through suitable connection with the forward end portion 2I of the shaft I5 causes the pistons I8 to be driven as pumping pistons, and the fluid distributor system operates in reverse from its operation where the device is used as a motor. That is, the hydraulic fluid is drawn in through one of the ports I9, 20 and is impelled under pressure from the other of such ports, depending upon the direction in which the shaft I5 is driven. Similarly as when the device is used as a motor, reversal of direction may be accomplished as nearly as practicable instantaneously and without any alteration in the mechanism or any adjustment required. In fact, the use of the unit either as a motor or as a pump is merely a matter of choice or expediency and is not dependent upon any adjustment or alteration in the mechanism. In both instances maximum efflciency, without any dwells, surging, lag or fluctuations in power output when the device functions as a motor, or in hydraulic fluid pressure when the device is utilized as a pump, will occur at any point in or between any cycle of operation as determined by a revolution of the shaft I5.

It may also be noted that throughout the unit the fluid distribution system provides passages and ports or orifices which are large in cross sectional area as compared with the respective piston areas. There is therefore a minimum of power loss from frictional resistance, the unit is cool running and of high efiiciency.

Any possibility of pressure binding and at- 9 :oendantdrag .nndfiriotional losses-within the unit due to .iuevitablegescape or leak by of high pressure fluid into non-pressure working areas of the unit, :is avoided by the provision of :a thorough scavenging system. system is so :arranged that complete self-lubrication of the working parts in the unit is accomplished. Also cooling of those parts which may be subject to frictional heating due to mechanical parts interaction during high speed, high pressure operation cites tively performed. Thus, by the present .invem :tion leak-by fluid which might otherwise create internal resistances and resulting power loss and .friotional heating of the unit, is actually .put to lgoodtnse andis maintained 2813 low, icon-obstruct ting pressure, "or even at negative pressure.

no the heart of the .scavenginggsystem are .means for relieving the "working area within the unit where the greatest potential leak-lay occurs ffrcm'the verynature of the operatingmechw ni'sm, namely the area-within which the pistons 4 8 operate. To '-this end, the piston shoulder clearance bores 28 and the connecting cam sleeve "chamber .11, treated as a leak-by reservoir chamber entity, as for :all practical ,purposes they are,

have relief communication'with the :low pressure or 'suction side of the .hydraulic :system of the unit, irrespective of the direction or motivation prevailing at any given time in then-nit. For this there is relief duct H110 communicating with the hydraulic .i'luid duct or passage to the "port is, and a relief duct 10:! communicating with the hydraulic nu'id duct or passage 4?! to the port 12 0. The relief ducts I00 and JBil are formed in the housing section 59 .At the rorward :face of the housing section 59 the ducts. 11:00 and tin have communication with respective slightly larger diameter relief ducts m2 and IE3, respectively, formed in the housing section and opening into the piston clearance chamber area. .A normally closed check valve 1104 in each of the relief ducts 102 and EH13 is biased by means such as a compression spring 05 to remain closed and to check high pressure :ilow of hydraulic ifiluid toward the piston clearance chamber area, but to respond to suction from the active hydraulic fluid circulation system of the or a combination of such suction and mild in t'ernal pressure created by the leak-by iiuid in the piston clearanoe chamber, for bleeding off excess leak-by fluid.

.It is preferred to maintain a reasonable supply of leak-by fluid in the piston clearance chamber ior lubrioating and cooling the pistons I 8 and "the cam ring c2 view of tnexrelatively close hearing relation of the shoulder portions of the pistons within the cam groove i3 3, even though by theconstruc'tion of the bearing surfaces :andthe rotational running of: the shoulders 25 the groove -during operation frictional resistance minimized -.Lubrication is eirected due to the islet that the shoulders i'2 5and the cam groove :33 are running in a :bath of the hydraulic fluid, which is customarily an appropriate oil In addition to cooling afforded by the at the outer face :of the cam ring 32, internal rcooliing..;is provided for through the medium of a communication bore Ill! which together with a here-$08 extends through the ring :32 and communicating with an internal annular groove we in the internal wall of the ring. The groove Hi8 cooperates with a complementary groove M ll in the supporting portion 58 0f the distributor tube orsleeve to provide :a coolant lcirculation channel .ililigfiros 4, 13 and 1a) By preference, th bores MW and 1-08 are formed at the opposite :side of the iring-3 2 .trom the internal keyway thereinand have the mouths thereof in proximity at the periphery of the ring. The bore m1 is prefer,- ably formed at a slight angle to the radius of the 32, tilted away from the mouth of the bore 108 approximatelyl0 from the sleeve radius. (3n the other hand, the bore 103 is preferably formed substantially tangential to the internal circulation groove 19 and til-ting toward the groove L01. This arrangement promotes coolant circulation through the groove 10'! in the rota.- tion of the cam groove ring. It facilitates entry of means such as a keying wire 108a (Figs. 4, 3 and ill) into the communicating portion of the passage 109-111] of the assembly to lock the ring 32 positively against axial movement relative to the sleeve 42.

Provision is made for draining off leak-by fluid from other parts of the operating mechanism to the piston clearance chamber, or on the other hand, delivery of the fluid to such parts f0rI11ibrieating purposes where an inadequate supply of hydraulic fluid leaks .by to such areas. To this end, the shaft 1 5 is formed in the distributor area 3.! thereof with longitudinal .grooves I I 1 (Figures .10, 1.1 and 12) which are disposed in the land areas between the fluid distribution grooves 38 to 41, inclusive. The rear ends of the relief grooves I ll open into the rear bearing chambers The front ends of the grooves ill extend Ffor a short distance into the bearing supporting area 35 of the shaft and have communication by way of end notch ports .l 41 .in the distributor sleeve 43 with the .front bearing chamber.

Communication between the grooves .l H and the piston clearance chamber at the operative center of the unit is effected through radial bores H3 (Figures 4 and -8) through the sleeve '42 one side of the cam sleeve supporting area 58. .In this fashion, leak-by fluid which may tend to accumulate in the bearing chambers will be drawn off through the longitudinal shaft grooves Hi "to the piston clearance chamber. On the other hand an equalization of lubricating fluid between the bearing chambers and the central piston clearance chamber is attained. Furthermore, this lubricating and .r-elief system is in dependent of the direction of hydraulic flow in the operating circuit since the relief system is at all times in controlled communication with the suction side of the system and the check valves HI-4 prevent entrance of pressure fluid into the scavenging system.

Fluid circulation between at least one of the relief grooves Ill and the coolant circulation portion of the annular internal keying fluid channel Hill-*1 :NJ may be provided for by a radial bore 114 through the sleeve portion 58 between the bottom of the groove H0 and the selected groove HI.

it will, *of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims. I

I claim as my invention;

1. a combination hydraulic motor or pump unit, a casing, :a shaft rotatable in the casing, longitudinal fluid distribution grooves on said shaft within the casing, a distributor sleeve coextensively encompassing the grooved portion of the shaft and the grooves to convert them ll into closed ducts, said sleeve having hydraulic fluid distribution orifices therein communicating with the grooves, the casing having means for communicating with a hydraulic fluid supply exteriorly of the casing and cooperating with the 1 distributor grooves and orifices to provide a fluid circuit within the unit, a plurality of pistons, and thrust transmission means carried by said sleeve and operatively coacting with the pistons,

said orifices having operative communication with the pistons, whereby when the unit is oper- "ating as a motor high pressure hydraulic fluid is supplied through said grooves and orifices for actuating the pistons and thereby driving the shaft through said thrust transmission means and when the unit is operating as a pump rotation of the shaft effects operation of the pistons ,through said thrust transmission means for "pumping the hydraulic fluid through said orifices and grooves.

2. A unit as defined in claim 1 wherein the thrust transmission means on the sleeve operatively coacting withthe pistons comprises ahelically grooved ring mounted fixedly on the distributor sleeve, and the pistons have interengroove comprises multl-helical portions effective to control relative movement of the pistons through a plurality of stroke cycles in each revolution of the shaft.

5. In combination in a hydraulic motor or pump unit of the character described, a casing "having means for communicating with a hydraulic fluid circuit, a shaft rotatably mounted in the casing, a plurality of longitudinal individual peripheral fluid distribution grooves in the intermediate portion of the shaft, said grooves being in straight coextensive parallelism for a portion of their length and thence extending in coextensive spiral direction about the shaft, a

sleeve about the shaft enclosing said grooves and isolating the grooves one from the other, a plurality of pistons disposed about the shaft within the casing, an operating connection between the shaft and the pistons, fluid supply and exhaust ports through said sleeve communicating with the hydraulic circuit communication means, and annular series of ports through said sleeve communicating with the grooves for hydraulic fluid distribution with respect to the pistons, one of said series of ports and said source communication ports being associated with the straight portions of the grooves and a remaining series of distribution ports being associated with the spiral portions of the grooves.

6. A unit according to claim 5 wherein the pistons are double acting and each having opposite end pressure heads, and the respective series of distribution ports in the distributor sleeve on the shaft communicate with the respective opposite ends of the pistons.

7. In a unit of the character described, a rotary shaft, a longitudinally extending annularly "spaced series of fluid distribution grooves on an intermediate portion of the periphery of the shaft, and a sleeve enclosing the grooved portion of the shaft in fluid-tight relation. and thereby closing off the grooves from one another, said sleeve having a plurality of annular longitudinally spaced series of fluid distribution orifices opening therethrough in communication with the grooves.

8. A structure according to claim 7 wherein said sleeve carries, intermediate a pair of series of distribution orifices, a cam ring for operative association with a set of shouldered piston elements.

9. A structure according to claim 7 wherein the shaft has grooves separate from the fluid distribution grooves and parallel thereto but extending beyond the ends thereof and serving as leak-by passages.

. 10. In a unit of the character described, a casing, a shaft rotatably mounted in the casing, a concentric series of pistons having opposite pressure ends and being operatively disposed within the casing about the shaft and having intermediate rib-like, radial, tapered annular shoulders, means defining pressure. chambers at the respective opposite ends of thepistons, lonegitudinally spaced annular hydraulic fluid com.- munication areas on the casing wall'communieating with respective portions of the shaft, the shaft having longitudinal hydraulic fluid distribution channel grooves in the periphery there of, an encircling sleeve on the shaft'closing said channel grooves from each other, ports through said sleeve communicating with respective ones of said channel grooves at said respective areas of hydraulic fluid communication, and IGSPBC-r tive series of ports through said sleeve communicating with the channel grooves and with said pressure chambers. 11. A unit as defined in claim 10 wherein the casing has a chamber affording clearance for 'l'eciprocal movement of the piston shoulders, and passages having pressure controlling check valves therein lead from said chamber to the respec tive hydraulic fluid communication areas.

12. A unit as defined in claim 11 wherein the shaft has additional leak-by grooves therein opening beyond the ends of said sleeve and having communication through said sleeve with said chamber.

13. A unit according to claim 12 including bearings supporting the shaft beyond the opposite ends of said sleeve, the casing having chambers therein accommodating the bearings, and the leak-by grooves communicating with the bearing chambers.

14. In combination in a unit of the character described, a casing, a shaft rotatable in the casing, a plurality of reciprocable pistons disposed in concentric series about the shaft within the casing, a chamber surrounding the shaft within the casing in the region of the pistons, annular follower shoulders on the pistons, and a cam ring encircling the shaft and secured fast -thereto, said cam ring and the follower shoulders being operatively associated, said chamber being normally adapted to contain hydraulic fluid in lubricating relation to the cam ring and the piston shoulders, said cam ring having an internal coolant flow channel and passage therethrough to said channel for circulation of the hydraulic fluid in cooling relation internally of the ring. 1

15. In a cam ring of the character described adapted tobe applied to a cylindrical support equipped with a longitudinal keyway and a circumferential keyway, the ring having a cylindrical bore to fit about the cylindrical support, said bore having longitudinal and circumferential keyways matching and complementary to the like keyways on the support, and a bore extending through the ring and running tangentially into said annular groove keyway in the bore spaced from the longitudinal keyway of the bore and adapted to' receive keying means therethro-ugh to hold the ring against longitudi-v nal movement relative to the support.

16. In combination in an overlapping thrust multi-piston motor or pump unit, a casing, a rotary shaft bearing in said casing, a plurality of pistons each having opposite pressure thrust ends, means within the casing about the shaft providing bearing bores for the opposite end portions of the pistons and disposed on parallel axes about the shaft, said casing providing a chamber about the shaft and the intermediate portions of the pistons, means on the pistons and on the shaft cooperative within said chamber and providing for thrust transmission between the shaft and the pistons, the casing providing means therein at the opposite ends of the pistons defining pressure chambers, means providing a reversible hydraulic circuit within said casing and communicating with said pressure chambers, said hydraulic circuit means including a pair of hydraulic passages communicating with openings to the exterior of the casing, and means defining a pair of passages within said casing communicating between respectively said externally communicating passages and said chamber and each including therein a check valve to prevent pressure fluid flow into said chamber but responsive to suction in the respective externally communicating passages for relieving pressure in said chamber.

17. In a unit of the character described, a rotary shaft, a series of longitudinally extending annularly spaced fluid distribution grooves on an intermediate portion of the periphery of the shaft and having the ends thereof terminating short of the respective opposite ends of the shaft, said shaft periphery intermediate said grooves having longitudinally extending leak-by passage grooves, and a sleeve enclosing the grooved portion of the shaft and entirely closing said fluid distribution grooves, said leak-by passage grooves extending beyond the opposite ends of the sleeve, said sleeve having fluid distribution orifices opening therethrough in communication with the re spective opposite ends'of said fluid distribution grooves.

18. For use in a multi-piston motor or pump, a rotary shaft, said shaft having a series of longitudinally extending annularly spaced fluid distribution grooves therein extending short of the respective opposite ends of the shaft, said grooves being throughout their length parallel to one another and each having a portion thereof extending parallel to the axis of the shaft and parallel to all of the remaining grooves and a portion thereof extending spirally into offset relation to the straight portion of the groove, a sleeve enclosing the grooved portion of the shaft and closing the grooves off from one another, said sleeve having individual orifices opening therethrough and communicating with the straight portions of the grooves and other individual orifices opening therethrough and communicating with the offset portions of the grooves.

19. In combination in a hydraulic motor or pump unit, a casing including means for accommodating a hydraulic fluid circuit, a shaft rotatable in the casing, a series of reciprocable pistons operatively mounted on parallel axes about said shaft, means providing cylinders for said pistons and cylinder head spaces in communication with said hydraulic fluid circuit accommodating means, thrust transmission means between said shaft and said pistons, said casing defining a chamber affording operative clearance for the thrust transmission means, said chamber serving also as a leak-by reservoir for hydraulic fluid escaping past the pistons into the chamber, and means defining fluid relief passageway leading from the chamber for communication with the suction side of the hydraulic fluid circuit.

ERNST F. ENGSTROM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,321,045 Hutchinson Nov. 4, 1919 1,603,228 Woerner Oct. 12, 1926 2,169,456 Wahlmark Aug. 15, 1939 2,215,700 Heideman Sept. 24, 1940 2,434,747 Ruben Jan. 20, 1948 

